Browser
A browser is a software application that is used to locate and display pages from the Internet. The two most popular browsers are Netscape Navigator and Microsoft Internet Explorer.
Browsers such as Navigator and Explorer are graphical browsers—they can display graphics and text. Also, they, and other modern browsers are directly capable of sound and video reproduction, or can be accessorized to permit the multimedia capability.
Browsers are able to direct queries to sites on the Internet because of hyperlinks--jumps to another place--whether a new position on the present page, a new page on the same site, another window that displays additional information, or an entirely new site. A hyperlink can be a Universal Resource Locator, or URL, which is the equivalent of an address. A URL often begins with ''http'', which refers to hypertext transfer protocol. Other parts of the URL address can specify the computer to which the request is directed, the domain name (the name of the institution housing the computer, for example), and, at the end of the address, a word followed by ''.htm'' or ''.html''. The latter are names of the file to return to the browser via the Internet.
The browser functions in the following sequence. The browser software sends the URL address to the relevant local area network or Internet service provider via a modem or network connection. The address is routed to the nearest domain name server, which returns a numerical address, called an IP address, to the browser and also sends out a request to a router--a special server that deduces the route that the message will take. A server at the site that contains the requested information receives the request from the domain name server. The server returns a signal acknowledging receipt of the request. Stored on this responding server is the web page of interest, stored as an ASCII text file marked with an identifier called hypertext markup language (HTML). When the server is able to respond, the HTML file is routed over the Internet, via the Internet service provider, to the computer from which the request was sent. The file is stored, or cached, as it is received--text arrives quickest, while graphics can take varying lengths of time to arrive. Icons in the upper right corner of the browser tool bar are active when the message is being received. When all the components of the message have arrived, the icon activity stops and the word "Done" appears on the status line of the browser window.
Browsers also permit a user to conduct a search of Internet sites by typing in words or phrases. When the enter key is pressed a search is carried out and the URLs of those sites that contain the key words are supplied as a list of hyperlinks. As sites are visited, their URLs are stored to provide a historical record of browser activity. If a repeat visit to a site is needed, the site address can be found in the history file and the hyperlink clinked to initiate contact with the site and downloading of information from the site.
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